INCAPE   05401
INSTITUTO DE INVESTIGACIONES EN CATALISIS Y PETROQUIMICA "ING. JOSE MIGUEL PARERA"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Fine chemicals synthesis: Selective hydrogenation of unsaturated nitriles to unsaturated primary amines
Autor/es:
ANDRÉS F. TRASARTI; CARLOS R. APESTEGUÍA; DARÍO J. SEGOBIA
Lugar:
Beijing
Reunión:
Congreso; 16th International Congress on Catalysis; 2016
Institución organizadora:
International Asociation of Catalysis Societies
Resumen:
The liquid-phase hydrogenation of unsaturated nitriles is an important route to obtain unsaturated primary amines that are valuable intermediates in aAgrochemical, pharmaceutical, and fine chemicals industries. Nevertheless, the selective hydrogenation of the CN group in unsaturated nitriles is still a challenging objective in heterogeneous catalysis1,2. In general, the hdrogenation of unsaturated nitriles may form three types of products: unsaturated amines (hydrogenation of CN bond), saturated nitriles (hydrogenation of C=C bond) and saturated amines (hydrogenation ofC=C and CN bonds). Besides, in order to obtain selectively primary amines, the coupling reactions leading to secondary and tertiary amines have to be avoided. Ammonia is often employed to suppress the formation of higher amines by shifting equilibrium to the primary amine since ammonia is released in the coupling reactions leading to secondary and tertiary amines;nevertheless, the addition of ammonia entails concerns related to corrosion and disposal of spent base materials. In this work, we investigate the selective hydrogenation of cinnamonitrile (CN) to cinnamylamine (CA) on silica-supported Co, Ni, Ru and Cu metals. As shown in Fig. 1, CN may be initially hydrogenated in the C=C bond to yield hydrocinnamonitrile (HCN) or in the CN group producing CA, probably via the formation of an imine intermediate (cinnamylimine). CA may then react with the imine intermediate to form by deamination the unsaturated secondary amine dicinnamylamine (DiCA) and partially unsaturated secondary amine hydrocinnamyl-cinnamylamine (HCCA). Otherwise, CA may be hydrogenated to the saturated primary amine (hydrocinnamylamine, HCA). Similarly, in parallel pathways, HCN may be hydrogenated to HCA or it may react with the imine intermediate hydrocinnamylimine) to produce by deamination the saturated secondary amine (dihydrocinnamylamine, DiHCA) and partially unsaturated amine HCCA. The activity and selectivity of silica-supported Ni, Co, Ru and Cu catalysts for hydrogenating CN to CA greatlydepend on the nature of the metal and reaction operating conditions. At 383 K and 13 bar H2, Ni/SiO2 is a very active catalyst that promotes the preferential hydrogenation of C=C bonds thereby forming mainly saturated nitriles and amines. Co/SiO2 is also a very active catalyst, but produces initially only small amounts of CA that are rapidly converted to saturated primary and secondary amines. In contrast, Ru/SiO2 and Cu/SiO2 catalysts are significantly less active than Ni/SiO2 or Co/SiO2 and deactivate during the progress of the reaction;however, both catalysts form mainly CA. The Cu/SiO2 activity, selectivity and stability for the production of CA may be remarkably enhanced by improving the Cu dispersion and increasing the reactor temperature and pressure. At 403 K and 40 bar, the Cu/SiO2-I catalyst yields 74% of CA from CN hydrogenation without the addition of any secondary amine formation suppressant such as ammonia.